The present invention relates to a linear slide, more particularly to a durable linear slide with a relatively large load bearing capacity and capable of high-precision linear movement.
Referring to FIGS. 1 and 2, in a first conventional linear slide 10, a sliding block 12 straddles a guide rail 11 and is movable back and forth along the length of the rail 11 by means of pairs of steel rolling ball trains 13 loaded on two lateral surfaces and an upper surface of the rail 11. Because the contact between steel balls and the surfaces of the rail 11 is by point, a straight linear path of movement for the sliding block 12 can be maintained. In other words, a high degree of precision can be achieved for the sliding movement. However, the service life of a steel ball is only about 50 Km, which impedes a continuous service of a desirable duration for the linear slide 10.
Referring to FIGS. 3 and 4, in a second conventional linear slide 20, a sliding block 22 also straddles a guide rail 21. The opposite lateral surfaces of the rail 21 are provided with grooves 23 of a V-shaped cross-section. Two cylindrical roller trains 24,25 are disposed in each of the grooves 23 at right angles such that the axes of the rollers in the two roller trains 24, 25 in the same groove 23 are at right angles, as shown in FIG. 4. Thus, the sliding block 22 is capable of moving back and forth along the length of the guide rail 21. Due to the higher rigidity and strength of the rollers (the expected service life of which is about 100 Km) of the roller trains 24,25 as compared to those of the rolling balls, the service life of this type of linear slide 20 is longer. However, when a positive force is exerted on the slide 22 as shown in FIG. 4, the lower roller train 25 bears a greater amount of the force because the contact surface in the direction of the force is larger for the lower roller train 25 than that for the upper roller train 24. Moreover, the lower roller train 25 flares towards the sliding block 22, and this renders the vertical parts of the latter to expand, thereby impairing alignment and precision of sliding movement of the linear slide 20.
In a third conventional linear slide 30 shown in FIGS. 5 and 6, a sliding block 32 also straddles a guide rail 31. The lateral surfaces of the rail 31 are respectively provided with a channel 311, and the sliding block 32 is provided with two pairs of grooves 321 opposing and adjacent to upper and lower sections of the channels 311. The grooves 321 constitute portions of circulation passages 33 for steel rolling ball trains 34, 35. By this structure, the sliding block 32 is allowed to move back and forth along the length of the guide rail 31. Since a pressure is exerted to the vertical parts of the sliding block 32 through the rolling ball trains 34, 35, the tendency to expand outward remains unresolved. In addition, the use of rolling ball trains 34, 35 as rolling elements entails an unsatisfactory shorter service life.